Improved bridge



FREDERICK Il'. cSMITH. OF BALTIMORE, MARYLAND, SSIGNGR T0 SMITH, LATROLEd: CO., OF SAME PLACE.

Letters Patent No. 96,278, daten October 26, 1,869.

.IMPROVED BRIDGE.

The Schedule referred to 'in these Letters Patent and making part of thesame.

To all whom it may concern.-

Be it known that 1 FREDRICK H. SMITH, of the city of Baltimore, countyof Baltimore, and State of Maryland, have invented certain new anduseful Improvements in the Construction ot' Bridges, and othertruss-trames; and I do hereby declare that the following is a full,clear, and exact description offthe same, reference heilig had to theaccompanying drawings, ina-king part ot this specification, in which-Figure 1 is a side elevation of that form of suspension-truss known asFinks.

Figure 2 is a side elevation of a beam-truss of the qlnnlrmlgular type.

Figure 3 is a side elevation of a beam-truss of the triangular type.

Figures 4, 5, and 6, are side view, section, and rear view ot' the.roller-bed', foot-box, and pin-joint at the end ot'l'Jeam-trusses,fhowing the attachment ot the lateral bracing and bottom chord to thepin.

Figures 'l' and S are side view and longitudinal section of the topchord at 'the joint, showing connect-ion of chord-strut aml lateralsystem at the pin.

Figures J and l0 are end views and cross-section thronghthe top chord atthe junction of lateral and vertical systems ou the pin.

Figures l1 and 12 are top view and horizontal section through the topchord, exhibiting the connections of lateral, vertical, and longitudinalsystems.

Figures 13 and 14 are side views ot' bottom chord, and adjusting-loop,and foot-box, showing connection of lateral bracing-systems t-o pins,and showing the method of riveting flanges upon the edges of thechord-bars.

Figures l5 and 16 are cud views, and cross-section through bottom chord,showing iianges riveted to chord-bars, and also connection of lateralsystems.

Figures 1 7 and 1S are cross-sections of bot-tom chords, showingchord-bars simply stit't'ened by blocks, and also where the anges arerolled upon the chord-bar instead of being riveted on.

Figures 19 and 20 are top view and horizontal section of bottom chord,showing connection of pin and laterals.

Figures 21,22, and 23, are side elevations of the same representativeforms of truss, substituting wood for iron in top chord.

Figures 24, 25, and 2li, are side elevations of the representativetrusses, with all eomljnessive strains taken up iu wooden struts and topchords; tension strains in iron.A

Figures 27, 2S, 2Q, and 30, are views on an enlarged scale of the:uljusting-lofms and foot-box.

M v invention consists iu- First, a novel and useful method of adjustingbeamtrusses, by taking advantage of the short line and -favorable angleofthe strut, instead of opera-ting upon the tie, as heretofore has beendone, and at the same time securing perfect freedom of action in thetruss by using the pin-joint throughout.

Second, a novel construction of bottom chord-bars, in which noenlargement of ends for eyes is required, as the bars are rolled thefull width required for the eye, and then st-ili'ened, so as to utilize,for the transverse strain of the load, all of what would otherwise besurplus metal in the bar; the st-itte-ning-proccss also furnishing aperfect bearing for the Hooi-ino.

Third, a novel attachment of the lateral bracingsysteins to thejoint-pins, by means of a bolt, which passes through the strap-loopsenclosing the nuts ot the lateral ties, through the strut which fitsover the end ofthe pin, and through the end ot' the pin itself, thussecuring facility of attachment, adj ustability, compaetness, a hinged'joint in the lateral planes of the bridge, and freedom from welds inany ofthe connections.

Fourth, a novel device for adjusting trusses of all kinds, by means ofloops or yokes bent over the pins, and having adjusting-nuts upon eacht'ork ofthe loops, upon which nuts the bottom plate ofthe strut issupported at its corners, thus virtually allowing the use of thesquare-end formula for columns, and giving extreme facility ofadjustment, and total absence of welds inthe manufacture ofthe loops.

To enable those skilled in the art to make and use my invention, I willdescribe the manner in which the saine is or may be carried into etiect.

In a truss composed entirely of wrought-iron, ecouolny is secured bycolicentrating the preponderance ot` strain in tension where thematerial is worth about twelve thousand pounds to every square inch ofsee'- tion, instead of taking it up in compression wherethe v materialis only worth about seven thousand pounds.

per inch.

This fact indicates atl once that the struts should be inclined, thusthrowing the heaviest strains into the bottom chord, and also shows thatthe economical angle, and consequent reach of the ties, are much greaterthan those of the struts. 1f the truss is to be raised or lowered byelongating or shortening the tie,

asis the usual custom, it is obvious that the resist ance to be overcomewill be much greater in the greatly-inclined tie than in theslightly-inclined struts and I- therefore abandon the tie, and apply theadjustnient to the strut, the means ot' adjustment being directlyapplied to the base or foot of the strut, thus admitting ol' thearrangement of the struts, not only in a vertical position, but at anydesired inclination, as shown in tig. 3, which would not be practicablewere the adjusting-devices applied, not directly to the strut, butthrough the flooring-system or other intermedia-ry. This at once avoidsthe necessity of using screws upon the ends of the main ties, thuspennitting the use ot' the pin-joint, combined with completeadjustability throughout the bridge.

'lhe necessity of a pin-joint is seen in the vpassage of a full-weighttrain across a three-hundred-feet-span beam-truss, during which theheads of the end struts are drawn about half au inch toward thespan-centre by the contraction of the top chord, while the feet ofthesamestruts are thrown about one inch away from the span-centre by theelongation of the bottom chord, thus iuclining the strut about one andonehalt' inch from the perpendicular or other original position. 'lhisdistortion of figure lmust sooner or later cause the crystallization ofthe iron, unless a hinge-joint is used.

In many bridges the pin-joint is used, but with no adjustment, and thelop-sided or sagging condition of most of these structures is the bestargument to prove the positive necessity' of au adjustment.

yIn my arrangement, the chords S are pierced at the joints, for the pinsa to enter, and both struts and ties take hold directly upon the pins,the 'top chord heilig recessed, as shown in figs. 7 and 9, to permitthese members to reach up to the pins, which in turn transfer theirstrain directly to the top chord, and not to the cheeks of a square box,inserted into the recess, as is sometimes done.

'lhe bottoms of the struts B have slotted holes l) in them, (sec iig.14,) or are otherwise forked over the pins ot' the lower chord, and aresupported squarely and firmly upon the nuts of the adjusting -loops r.

The adjustmentiselbcted by turning these nuts, thus drawing the pinupward or downward in the slotted hole, and thereby increasing ordecreasing the distance between the pins at the diii'erent ends of thestrut, and virtually making the strut longer or shorter, as may berequired. y v

The ticsG also take hold of the pins of thebottom chord, and, in commonwith the strut, have full liberty to turn upon the pin.

ln constructing the bottom chords of bridges, the

method usually followed is to use flat bars, with enlarged ends, toreceive the pins, this enlargement heing a very expensive process, andliable to insecurity from welds, unless the upsetting-process is used.

In some instances the cross-ties of the bridge have been laid directlyupon the edges of these eye-bars, their number being increased to meetthe transverse strain, but the general plan is to suspendcross-licorbeams from the pins, and lay stringers, Snc., upon them.

This makes it necessary to put the line of lateral bracing below thecentre lineof the chord, and leaves t-he structure liable to greatvibration.l

In my arrangement the tension-bars I) are not really eye-bars, but aresimply rectangular bars, of the tulL width of the eye.

The piu-hole is -drilled out, and the available sec tion thus left isapplied to resist tension-strains in the chord, while the remainingsection in the body of the bar, which would otherwise be surplus metal,is used 'to resist the transverse strain arisingi'rom the passage of theload, the bars being stiiiened between the points of support, in orderto resist this strain more etlectually, and also to aord a broadersupport to the'cross-ties E than would be oered by the simple edge ofthe bar. v

'lhis stitfcning is done by riveting flanges d to the upper or bothedges of the bar, or by inserting pack ing blocks between the bars, withbolts oi' rivets through them, and placing the cross-ties upon theln.

The flanges 'can be rolled upon theI original bars, as seen in iig. 18,instead of being riveted to them, if de sired.

In long spans, where the chord-strains are very heavy, the amount ofsurplus metal would be much more than could be utilized, were all thebars rolled full width, and in these cases a suiicient number of widebars is used, and the remainder of the requisite section for tension ismade up by placing ordinary eyebars upon the pin.

This arrangement brings the point of application of the transverse loadas nearly as possible to the cen tre line of the cord, thus reducingvibration.

It will further be noticed that the tension or chordbars D are arrangedalternately in pairs and single bars, the ends of the latter littingbetween the ends of the former, and each three ends, which thus meet,being jointed upon the pins a.

The hars which are in pairs have an angle or stiffenlng-iron insertedbetween them, while the single barshave the stieningdrons o'n each side.

The chord is thus made completely adjustable at any desired point, whileat the same time it preserves the strength requisite for the purpose forwhich it is designed.

Heavy ,guard-stringers F are notched over and bolted down to thelcross-ties to perform t-he double duty of preventing displacement ofties during accidents, and also to distribute t-he load fore and aft.

'lhe pins in both top and bottom chord have screws and substantial nutsf upon their outer ends, and their inner ends project several inchesbeyoudthe chords, &c.

lhe lateral struts G fit over the projecting ends of the pins.

The lateral ties H have screws, and nuts upon their ends, and pass intostraps or loops, which fork over the. ends ot' the lateral struts. 4

A bolt, g, passes through loops, strut, and pin, and the wholecombination is then. drawn up to a tight and compact jointby the nutfupou the outer end of the pin. v

'lhc bolt gives freedom of motion for expansion and contraction, insympathy with the motion of the chord, and the lateral ties H areadjusted, by means of the nuts upon their ends, within the'loops.

In order to show the adaptation of the foot-adjustment, as used in myarrangement for the beam-truss, to a suspension-truss, I will note thepoints of diierence between my loop and other devices Vthat arc used inthe feet ot' suspension-trusses.

In the bridge patented and built by Bolhnau there is a link whichclosely resembles mine. in appearance, but ditfers very essentially inthe fact that it is composed of a single eye-bar, with a screw upon theend, this screw supporting thepost directly under its centre-line, andnecessitating' the use of the formula for columns with rounded ends.

The wedge-system, used by the patentee of the Fink truss, is also opento the same objection, as it supports its load above the pin, and isalso liable to fatal displacement of parts by 'sudden shocks.

My loop supports the post at the four corners of the footplate, entirelybelow the pin, and the loop itself is simply a bar bent over the pin,requiring no welding as does the Bollman link.

In cases where the. diameter of the strut is very great, a collar isplaced around the pin, in orderto spread the two arms of the loop apart,and thus ob tain the widest possible base ot' support.

The adjusting-loop and foothox are represented ou au enlarged scale, inrigs. 27, 28, 29, and 30.

The pin a is set in the slotted foot-box of the strut B, and carries oueach side the ties G.

The loops A tit over the pin, and their lower screw` threaded ends passdown through the base ofthefootbox, and are provided with nuts c c, byturning which the working-length of the strut may be iuereasedorAdiminished, as before specified.

While preferring the use of the adjusting-devices described, other meansmay be employed for the puri.

' or their mechanical equivalent, applied directly to the foot or baseof said post, for the purpose of contreating or elongating itsworking-length, substantially as set forth.

2. The arrangement of the chord-bars, provided at Itheir upper edge oredges with `iianges or sti`eningirons, for the purpose specied, andjointed to the pins' upon which 'their ends are supported, substantiallyas shown and set forth.

3. The attachment of the lateral bracing-systems to the jointpinsfbymeans of the holt which at once combines the pin, strut, loops, and'adjustable ties finto a hinged joint in thelateral planeof the truss,

substantially as .shoW11'and.lspecified.

4.,I`he combination, with the feet of the struts or posts, of theadjusting-loops and joint-pins, with which 111e lateral bracing-systemis connected, substantially as herein shown and set forth.

In testimony whereof, I have signed my name to this specification,before two subscribing witnesses. FREDERICK H. SMITH.

Witnesses:

EDM. F. BRoWN, M. BAILEY.

